Platform and processor power management

ABSTRACT

The present invention relates to platform power management. In some implementations, platform tasks, that require servicing by a host processor, may be serviced in groups to create longer or more idle periods to enable the host processor to be in lower power consuming states more often.

TECHNICAL FIELD

The present invention relates generally to computing systems and inparticular to platform management methods and systems.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example, and notby way of limitation, in the figures of the accompanying drawings inwhich like reference numerals refer to similar elements.

FIG. 1 is a diagram of a computing system in accordance with someembodiments.

FIG. 2 is a flow diagram of a routine for synchronizing tasks for a hostwhen it is to be awoken in accordance with some embodiments.

FIG. 3 is a flow diagram of a routine for initiating a host mode abasedon a received network device idle notification in accordance with someembodiments.

DETAILED DESCRIPTION

Mobile platform computing devices, e.g. laptops, tablets, cell phones,and mobile internet devices (MIDs), offer ubiquitous networkconnectivity through one or more communication interfaces. Most of theseplatforms' usage models are driven by communication activities. Whilecommunication devices themselves consume a relatively small portion ofthe platform power, the impact of communication usages on the overallplatform power can be significant due to the non-deterministic nature ofthe incoming/outgoing network traffic, which may keep the platformactive in higher power consuming states more than necessary.

Network task activities are typically initiated by applications usuallybased on timer expirations to wake up the host in order to generateoutgoing messages. In the past, if the platform components were in adeep sleep state, e.g., lowest C state (i.e., C5 or higher) for theprocessor and similar lower level platform power state, then thisactivity to send non-time-critical packets would cost significantamounts of power as they would prevent the full platform to reach orremain in lower power states. To make matters worse, the applicationsgenerally operate independently based on their own timers, withoutknowledge of the platform or other application operations. As a result,the platform would wake up at random times to process tasks issued fromthe different applications, preventing the platform from reaching andstaying in the low power states.

In some embodiments disclosed herein, interfaces and mechanisms arepresented for applications that require network keep-alive, periodic andnon-time-critical network access to sync-up with the platform activitiesand with each other in order to create longer periods of idleness forthe platform. For example, to maintain the application's “heart beat”while waking-up the platform for a minimum number of times,non-time-critical outgoing network activities may be synchronized, asallowed within the limit of the most stringent timing requirements.

As platforms move to the use of so-called “tickless” operating systems(OS), it becomes desirable to control outgoing network trafficactivities and coordinate them with platform activity to fully benefitfrom longer term idleness, which may allow platform components to reachdeeper sleep states, thus increasing battery life.

FIG. 1 shows a computing system in accordance with some embodiments.This diagram illustrates an architecture for implementing platform powermanagement. The system comprises a platform 102 with peripheral devicesincluding a hard drive 122, mouse 124, keyboard 126, and networkinterface devices 128. The platform 102 includes at least one processor110 and platform control hub 105, coupled as shown. Also included is apower management unit (PMU) 112, which in this embodiment, is part ofthe processor 110. (A power management unit may be implemented as aseparate processing unit in a separate chip or in any suitable chip inthe platform. In some embodiments, it may be implemented as a separatecontroller within the processor or in another chip such as the PCH 105.)The processor and/or PMU execute an operating system (OS) 140, alongwith applications 131. In the depicted embodiment, the OS (e.g., in userspace driver, patch, or equivalent) implements an OS applicationinterface 142 and OS platform interface 144 for identifying tasks to beperformed on the application and platform sides, respectively. An OSmessaging register 141 is set up to store task information (e.g., taskqueues, timers, etc.) for efficient performance coordination.

The applications 131 represent applications such as instant messaging(IM), internet widget, email, and other applications that have networkactivity (periodic or otherwise) without necessarily having userinvolvement. These applications typically send out keep-alive messagesperiodically to prevent connectivity from timing-out, and pull updatedinformation e.g. email in box status, weather report, stock changes etcfor the widgets and the like.

The PMU 112 may perform various different functions including managingthe platform, as well as managing its activity state. In someembodiments, the platform activity state is independent from theactivity state of the processor. For example, the processor may be in aso-called “C” state (as defined by the Advanced Configuration PowerInterface, ACPI, standard) whereby C0 is the most active state, whilelower activity states (e.g., C1 to C7) define different levels ofreduced activity and thus reduced power consumption. At the same time,the platform may be in its own power state, e.g., ranging from a higheractivity state to lower level sleep states. In some schemes, S0 is thehighest activity platform state, while S3, S4, and S5 indicateprogressively lower activity platform states. In some embodiments, whenthe platform is in an S0 state, network communications and otherplatform activity may occur, even when the processor is asleep, i.e., ina lower C state.

The OS App. interface 142 enables the applications to register with theOS service to synchronize the outgoing network requests (i.e.transmissions). This OS level feature enables the pull-in of tasks thatwould be expected to be run within the next period of quietness in orderto run them sooner, assuming their jitter” requirements are withinbound. This works to make the platform more quiet to enable longeridleness.

The OS platform interface 144 is an interface between the platform andthe OS. Through this interface, the platform informs the OS of expectedperiod(s) of quietness. For example the network interface(communication) device 128 informs the OS-platform interface via the PCH105 of expected idle durations and holds incoming traffic on thecommunication device. The duration may be estimated through heuristicsor other means. Similarly, the other peripheral devices may instruct theinterface, via the PCH, about their quietness duration, and then the PCHcan notify the OS through this interface.

In some embodiments, applications having non critical outgoing messagesdeadlines or engaging in periodic network activity register with theOS-application interface for coordinating application task and platformactivities. The provided information may include, for example, messagefrequency and timing requirements including allowable jitter.

In the depicted embodiment, the PMU 112 executes a platform managementroutine 114, which among other things, coordinates the processing ofapplication and/or platform tasks that must be performed, even when theprocessor is at a lower activity state. FIGS. 2 and 3 (discussed below)show different routine functions that may be performed as part of aplatform management scheme. In some embodiments, they may be executed aspart of a platform management routine 114 in a PMU 112.

FIG. 2 shows a routine 201, which may be run or initiated by a platformmanagement program such as PM program 114, for coordinating taskapplication and platform task processing when a processor is in a sleepmode. Initially, at 202, the OS-application and OS-platform interfaces(or equivalents) are initialized or updated with application timer andplatform idle duration (e.g., estimated idleness) information. Regardingplatform information, the platform may predict the incoming period ofidleness based on various factors. For example, predicted idleness couldbe based on information from peripheral devices. Incoming idle durationscan be detected by the PCH and/or PMU when the peripheral devicesindicate that there won't be activity for some time, e.g. thecommunication device buffering the data for the next 50-100 ms. Idledurations may also be predicted using adaptive estimation approaches,e.g., based on heuristic idle durations. For example, an exponentialfilter could be applied to estimate the incoming idleness based on pasthistory of idleness duration.

Next, at 204, the routine determines if there is platform activity. Forexample, if a user is attempting to interface with the platform throughone or more of the peripheral devices, this would be caught here. If theplatform is not active, then the routine proceeds to 206 to determine ifany application timers have expired. If none have expired, indicatingthat application tasks are not needing to be serviced, then the routineloops back to 204. Otherwise, if one or more application timers has goneoff, then the routine proceeds to 208 where it wakes up the host toprocess the task corresponding to the expired timer. From here, it goesto 220 and checks other applications and/or application timers, e.g.,applications with keep alive messages needing to be periodicallycommunicated.

At 222, it checks to see if any of these application timers will expiresoon, e.g., within a predicted platform idleness duration. If so, thenat 224, it processes the task(s) and goes to 226 to check applicationqueue(s) for applications with non time critical tasks to be serviced.At 222, if the keep alive app. timers were not to go off soon, then theroutine would come to 226 directly.

At 228, it checks to see if the non-critical app. queue is empty or hastasks to be processed. If there are tasks, they are processed (orserviced) at 230 thereby extending the idleness period even further. Theroutine then goes to 232 and initiates the host to go back to sleep, andloops back to 204. If the queue is empty at 228, then it goes right to232 and proceeds as described.

Returning back to 204, if there is platform activity, then the routineproceeds to 210 and wakes up the host (processor). From here, it goes to212 and informs the OS and then goes to 214 and checks timers forapplications with periodic pulling messages. When the OS is informed andthus active, i.e. has been woken-up by an event like an interrupt orincoming packet, it checks those applications with transmit activityrequirements and checks if their timers are close to expire.

If, at 216 it is determined that any are to go off soon, then at 218they are processed, and the routine goes to 220. If none were to go offsoon, then the routine would proceed directly to 220. From here, itproceeds as discussed. The OS notifies those applications to perform thetransmission. Then the timer is reset so those applications will notwake up the platform for the next period of quietness. (As when theplatform detects an incoming period of quietness, the PMU or PCH mayalso notify the OS of an expected quietness duration. In this case, theOS may try to pull-in the transmit requests that might expire laterduring the idle period and get the transmission started.)

FIG. 3 shows a routine 301 for affecting the primary component in thehost, namely, processor, to be in an activity state based on expectedidleness as gleaned from a peripheral or network device. The basic ideaof this routine is that the communication device (e.g., peripheraldevice or network interface device) informs the host of the estimatedincoming idle duration, and the host then makes an “informed” decisionas to which power saving state to enter based on this information, aswell as possibly other platform activities.

Initially, at 302, the platform managing entity receives an idlenotification from a communication (network interface) device. Forexample, an idle notice could come from a network agent such as with anetwork interface card (NIC) such as is taught in U.S. patentapplication Ser. No. 12/283,931 entitled SYNCHRONIZATION OF MULTIPLEINCOMING NETWORK COMMUNICATION STREAMS, filed on Sep. 17, 2008 andincorporated by reference herein.

At 304, it checks to see if there is any other platform activity that ismore frequent than the notified idle duration from the communicationdevice. If not, then at 308,1 it compares the notified duration [T(n)with the host break even duration [T(b). Ideally, if expected idlenessis long enough, the host can be initiated to enter a deeper sleep state(e.g., CPU c5, c6, or C7) whereby its cache is flushed and increasedpower may be saved. Thus, the break even duration corresponds to thecosts (latency, power, etc.) associated with entering such a state. Ifthe notified duration is smaller than this break even duration, it islikely not worth it to enter such a deeper state.

Accordingly, at 310, if the routine determines that the notifiedduration is less than the break even duration, then it goes to 312 andcauses the host to stay in its present state or places it in arelatively shallower state of inactivity. On the other hand, if thenotified duration is greater than the break even duration, then theroutine goes to 314 and causes the host to go into a deeper state ofinactivity, e.g., whereby its cache is flushed and significantly lesspower is being consumed.

Returning back to 304, if the routine determined that other platformactivity may occur that would interrupt or interfere with the notifiedidleness, then the routine goes to 314 and makes a determination basedon the platform activity.

An advantage of this approach is that with existing approaches, CPUscheduling logic causes the CPU to enter deep (e.g., C5, C6) states onlywhen the cache is empty. And it may take several attempts for the CPU toshrink the cache completely. Thus, the CPU often stays in shallow powersaving states for unnecessarily long times. With the routine of FIG. 3,however, the host (CPU or processor) can shrink the cache in a singleattempt and go into a deep power savings state immediately if theincoming idle duration is longer, for example, than a C5 or C6 breakeven time. By doing this, the host may achieve significant powersavings.

It should be appreciated that various mechanisms can be used to conveythe idle notice information from the device(s) to the PMU or host. Forexample, a PCIe extension could be used. Extensions to the PCIe could bedevised so that devices can transfer their resume latency informationrequirements, e.g., as defined in a platform interface scheme. Anadditional field carrying the “idle duration” could be added for futureversions of the interface. Additionally, extensions could be defined foruse in devices including network devices such as wireless NICs tocoordinate activity with the PCH. Memory and/or I/O triggers could beused. This is more of an ad-hoc approach, but a memory/IO mappedregister could be used to signal this idle information between thecommunication device and the host. Intelligent host estimations, e.g.,based on NIC capability, could also be employed. Network device(s) canset a registry entry informing platform that it will perform trafficregulation (e.g., Smart-FIFO) with the relevant parameters (e.g., buffersize, intended buffering time). The host or PMU could read thisinformation when the device is enabled. If the NIC device changes itsbehavior, an interrupt could be generated so the PMU or host can updatetheir policy accordingly. With this information from the NIC, the host(or PMU) observes the interrupt pattern from the network devices andestimates the incoming idle duration. With this knowledge, the host isable to take actions described above for optimal power saving.

In the preceding description, numerous specific details have been setforth. However, it is understood that embodiments of the invention maybe practiced without these specific details. In other instances,well-known circuits, structures and techniques may have not been shownin detail in order not to obscure an understanding of the description.With this in mind, references to “one embodiment”, “an embodiment”,“example embodiment”, “various embodiments”, etc., indicate that theembodiment(s) of the invention so described may include particularfeatures, structures, or characteristics, but not every embodimentnecessarily includes the particular features, structures, orcharacteristics. Further, some embodiments may have some, all, or noneof the features described for other embodiments.

In the preceding description and following claims, the following termsshould be construed as follows: The terms “coupled” and “connected,”along with their derivatives, may be used. It should be understood thatthese terms are not intended as synonyms for each other. Rather, inparticular embodiments, “connected” is used to indicate that two or moreelements are in direct physical or electrical contact with each other.“Coupled” is used to indicate that two or more elements co-operate orinteract with each other, but they may or may not be in direct physicalor electrical contact.

The invention is not limited to the embodiments described, but can bepracticed with modification and alteration within the spirit and scopeof the appended claims. For example, it should be appreciated that thepresent invention is applicable for use with all types of semiconductorintegrated circuit (“IC”) chips. Examples of these IC chips include butare not limited to processors, controllers, chip set components,programmable logic arrays (PLA), memory chips, network chips, and thelike.

It should also be appreciated that in some of the drawings, signalconductor lines are represented with lines. Some may be thicker, toindicate more constituent signal paths, have a number label, to indicatea number of constituent signal paths, and/or have arrows at one or moreends, to indicate primary information flow direction. This, however,should not be construed in a limiting manner. Rather, such added detailmay be used in connection with one or more exemplary embodiments tofacilitate easier understanding of a circuit. Any represented signallines, whether or not having additional information, may actuallycomprise one or more signals that may travel in multiple directions andmay be implemented with any suitable type of signal scheme, e.g.,digital or analog lines implemented with differential pairs, opticalfiber lines, and/or single-ended lines.

It should be appreciated that example sizes/models/values/ranges mayhave been given, although the present invention is not limited to thesame. As manufacturing techniques (e.g., photolithography) mature overtime, it is expected that devices of smaller size could be manufactured.In addition, well known power/ground connections to IC chips and othercomponents may or may not be shown within the FIGS, for simplicity ofillustration and discussion, and so as not to obscure the invention.Further, arrangements may be shown in block diagram form in order toavoid obscuring the invention, and also in view of the fact thatspecifics with respect to implementation of such block diagramarrangements are highly dependent upon the platform within which thepresent invention is to be implemented, i.e., such specifics should bewell within purview of one skilled in the art. Where specific details(e.g., circuits) are set forth in order to describe example embodimentsof the invention, it should be apparent to one skilled in the art thatthe invention can be practiced without, or with variation of, thesespecific details. The description is thus to be regarded as illustrativeinstead of limiting.

What is claimed is:
 1. An electronic device, comprising: a host arranged in a lower activity state; and a platform management unit (PMU) operative to manage a platform comprising components with tasks to be serviced by the host, the platform arranged in a lower activity state independent of the lower activity state of the host, the PMU operative to cause non-time-critical tasks to be serviced during a wake-up time for the platform when tasks that cause the platform to wake-up are serviced to extend platform idle durations, the non-time-critical tasks comprising one or more of network keep-alive, periodic or outgoing network communications for one or more applications.
 2. The device of claim 1, in which the tasks causing the platform to wake-up comprise application tasks initiated with a timer.
 3. The device of claim 1, in which the PMU is part of the host.
 4. The device of claim 1, in which the PMU is part of a hub block apart from the host.
 5. The device of claim 1, in which the platform components comprise peripheral components and network interface components.
 6. The electronic device of claim 1, the PMU operative to receive information regarding the frequency and timing requirements of the non-time-critical tasks.
 7. The electronic device of claim 1, the host operative to empty a cache in a single attempt.
 8. The electronic device of claim 7, the cache comprising one or more non-time-critical tasks.
 9. A method comprising: in a platform lower activity state, determining if there is platform activity to be serviced; if there is no activity to be serviced, determining if an application task requires servicing; and if an application task requires servicing, waking up a host and causing the application task to be serviced and while the host is still awake, servicing other tasks, the other tasks comprising one or more of network keep-alive, periodic or outgoing network communications for one or more applications.
 10. The method of claim 9, wherein servicing other tasks comprises determining if any other application timers may expire in a predetermined time duration.
 11. The method of claim 10, wherein servicing other tasks comprises determining if any non-time-critical tasks are awaiting servicing.
 12. The method of claim 9, comprising putting the platform back into the lower activity state.
 13. The method of claim 12, comprising putting the host back to sleep after the tasks are serviced.
 14. The method of claim 9, comprising: emptying a cache comprising the other tasks in a single attempt.
 15. A method comprising: receiving a task to be serviced by a host; determining if the task can be put off for at least a break even duration if the host is in a sleep state; putting the host in the sleep state and delaying servicing of the task if the task can be put off for the break even duration; determining if other tasks need servicing before the break even duration and not putting the host in the sleep state if the other tasks need servicing before the break even duration.
 16. The method of claim 15, in which the sleep state involves flushing cache associated with the host. 